The design of reinforced concrete deep beams is not yet covered by the current British Code CP110: 1972. Some provisions are given in the CEB-FIP Recommendations (1970) and the AC1318-71 Building Code, and the new (1977) CIRIA design guide contains more comprehensive guidance including a number of recommendations for the design of deep beams with web openings. This thesis is concerned with the general behaviour in shear of single-span reinforced concrete deep beams and in particular the effects of web openings on their ultimate strength and serviceability. The test specimens comprised seventy-five lightweight and sixteen normal weight reinforced concrete deep beams with span/depth ratios ranging from one to two. The effects of a varied range of web openings on deflections, crack widths, cracking loads, failure modes, and ultimate shear strengths were studied, and the influence of web reinforcement was investigated. The exact analysis of reinforced concrete deep beams with web openings presents formidable problems. However, the ultimate shear strengths of such beams can be predicted with reasonable accuracy using a simple structural idealization, which was derived from the results of the test programme. A simple design method is explained and design hints are given. The procedures currently used by practising engineers for the design of deep beams are outlined and discussed, and a more detailed review of the new CIRIA guide is presented. Design examples are given to illustrate the use of the various methods. In all the current procedures, the design assumptions regarding the anchorage requirements of the longitudinal tension reinforcement are necessarily conservative. Appendix 1 describes the details of nine tests carried out to provide information on the effects of various amounts of end anchorage on the strength and crack, control of deep beams. In Appendix 2 details are given of three tests carried out to investigate the behaviour of deep beams under repeated loading conditions.

Sustainable development is gaining popularity around the globe nowadays. Governments are under pressure, on many fronts, to embed sustainable development in policies, practice, and operations to secure the planet's future. Adding to this, increased populations, and the need for more infrastructures, have unfortunately led to the unacceptable depletion of raw materials, increasing amounts of construction and demolition waste (C&DW) and accelerated deterioration of the natural environment in many places worldwide. For the conservation of natural resources, reuse and recycling of C&DW is the most obvious way to achieve sustainability in the construction sector. Currently, recycled aggregate (RA) is produced from C&DW in modern recycling facilities, under good quality control provisions which could lead to improve its performance compared with the earlier days of recycling. In addition to C&DW, large amounts of industrial and mining by-products such as fly ash, slag, limestone powders, aggregate dust, etc. are dumped in landfills. Fly ash has been used successfully in concrete for a long time due to its numerous advantages across a wide range of properties, including aspects of durability. A concrete produced with the combination of PFA and RA i.e. recycled aggregate concrete (RAC) is obviously more sustainable and economical than conventional natural aggregate concrete (NAC). To date, statistics show that a considerable proportion of the world's RA is used for low-utility applications due to perceived risks and uncertainty over their performance formed as a result of previous history of use when RA was produced manually and low strength cement and higher water to cement ratios were used. Despite the advances in recycling, materials and concreting technologies, this impression prevails. However, to increase the use of RA, it is believed that the quality of RAC should be improved by chemical and mineral additives. For cost effectiveness, quality-improving additives should be abundant, safe, and inexpensive; PFA and new generation polymer-based superplasticizer (SP) are deemed to be a good option. The aims of this study are to investigate the possibility of producing good quality RAC that could be used as a substitute for NAC in normal strength concrete members, and to study its fundamental properties. An attempt has been made to create superplasticized RAC concretes, in which new generation polymer-based SP and PFA produced to the latest European standards were used. PFA was used to partially replace fine aggregate and cement in ordinary and self-compacting concretes. The thesis also includes an investigation into the potential of utilising an aggregate by-product (red granite dust (RGD) in producing environmentally beneficial RAC. The findings show that good performance RAC can be produced with the help of SP and PFA. The study also revealed that it is possible to utilise RGD to substitute up to 30% of cement without substantially influencing the performance of concrete, while also providing cost savings. Strengths and stifnesses of the ensuing RAC either with SP, PFA, or RGD were comparable, or better than, a wide range of counterpart NACs. The author's produced RAC concretes can replace NAC concrete used unnecessarily for many applications including structural concrete.

There has been a consistent discrepancy between UK design standards BS5400 and BS8110 in the prediction of the shear capacity of 2-way spanning reinforced concrete pile caps from bending theory-based empirical design formulae. This causes designers difficulty to predict an accurate shear capacity of the pile cap. The inherently empirical character of the formulae is due to the fact that the formulae have been extrapolated from semi-empirical shear formulae for simply supported deep 1-way spanning beam structures, and been further empirically developed for 2-way spanning caps. Thus the essential cause of the discrepancy is that the formulae lack both physical explanation in terms of the cap’s shear behaviour, and sufficient basis as empirical formulae due to the shortage of experimental data. This research focuses on the revelation of the true shear capacity and failure mechanism of pile caps by consideration of a particular prototype form, namely a singly reinforced four-pile concrete cap under wall loading. It is aided by a series of laboratory experiments which are validated by an advanced non-linear numerical modelling for the reinforced concrete structure. The experience from the numerical modelling is taken further to carry out a parametric study expanding the sample size to a range covering more practical samples and covering different load patterns in order to enrich the limited data from the experiments. The results give a verdict that both BS5400 and BS8110 are conservative with the former one most conservative. The level of conservatism of the standards, the actual shear capacity and failure mechanism of the cap vary with key pile cap dimensions such as longitudinal and transverse pile spacing, shear enhancement factor, and the width of the cap over which the shear enhancement factor is applied. The shear behaviour of pile caps is also influenced by the load patterns. In this research, the strut-and-tie method has been proved to be a more efficient and precise method than the empirical formulae because it presents a physical explanation of the shear mechanism. Suggestions to improve the design method are given. A particular feature of this research is the application of a digital photogrammetry technique (PIV), normally applied in soil and fluid mechanics, to a solid mechanics situation. The tool has successfully detected the full-field displacement on the concrete surface and strains which are of high magnitude. The outputs have been compared with those from numerical modelling and they are in the same order of magnitude. The thesis describes the procedure of the application and an analysis of errors expected to occur in its application.

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Inevitable flaws in the concrete-FRP interface govern plate debonding, and are not amenable to finite element analysis because the models require far more detail than will ever be available for the interface. This thesis describes a global-energy-balance based fracture-mechanics model for the debonding mechanism of externally bonded FRP plates attached to concrete beams. The model investigates the possible propagation of an existing interface crack by considering the energy balance of the beam during a small potential crack extension. The crack will extend if the energy release rate is greater than the interface fracture energy. Despite the fact that the crack-tip stress field is not amenable to precise analysis, its influence on the energy balance of the beam is insignificant because of the small volume of the "uncertain zone", whereas the crack tip stress field would solely govern an analysis based on linear elastic fracture mechanics. The plate end and the locations where the widening of flexural and flexural/shear cracks cause interface flaws are the most likely locations for the initiation of debonding. The model analyses debonding that initiates from either location. With the small extension of the interface crack the compatibility between the beam and the FRP alters, consequently causing changes in the stress states, and hence the energy states, of zones in the vicinity of the crack. The change in energy state of a beam section upon interface crack extension is determined from a modified version of Branson's model. The strain state when the FRP is fully or partly debonded needs to be considered. The mechanics of stress transfer from the concrete to the FRP differs from that with conventional steel reinforcing bars for which the accuracy of the original Branson's model was validated. So, the moment-curvature model considers the force in the FRP as an external compressive force on the concrete beam section; the separation of the effects of the axial force and the moment is achieved by defining an equivalent centroid. Debonding will propagate in whichever of the concrete, adhesive, or at an interface that provides the least resistance; thus, the interface fracture energy is that of the weakest phase. Experimental observations confirm that the concrete substrate just above the interface is most likely to fail, in particular when the FRP manufacturer-recommended adhesives are used with appropriate curing procedures. Fracture energy of concrete is determined from Hillerborg's cohesive-crack-model-based experimental and approximate theoretical models. Premature debonding propagation within the adhesive layer can also be analysed but the knowledge of that fracture energy is required. The energy release rate is calculated for assumed interface crack lengths and locations, from which the critical state is determined when it equals the interface fracture energy. Comparisons with test data reported in the literature demonstrate that the model is accurate for all modes of plate debonding. The analysis gives the critical plate curtailment location and the critical crack length which trigger debonding at the plate end and in the high moment zone respectively. The model allows for the inclusion of all properties of the concrete beam, adhesive, FRP and the loading arrangement and hence can be used as an optimisation tool in design. The model also provides a framework for the design of more complex real -life applications, and highlights subjects that require further research.

The nature of this research is in advancing conventional structures and their methods of construction by exploring new technology. The formwork construction of the modern concrete structure involves the use of rigid materials such as steel and timber. This type of formwork often produces structures of forms with limited flexibility which would also hinder the even distribution of the induced stresses. To construct concrete structures with more organic forms; ones that responds to a more natural flow of the induced stresses, it is thought to be more logical to use flexible mould such as the fabric formwork. In such form-active shape the materials’ utilization can be maximized and the degree of material waste can be reduced. For example, when the form responds to the externally applied loads in the way that the internally incurred stresses at any point of the body closely match the capacity of the material, then the form is material-efficient and said to be in its optimal form. The use of fabric formwork, due to its permeability can also improve the quality of concrete by eliminating any air holes on the surface, and also there are reports showing the increase in concrete’s compression strength due to the reduction in water-cement ratio when cast in a fabric mould. This research concentrates on finding such material-efficient form (thus more sustainable) for reinforced concrete beam of improved material quality, through the development of the more efficient construction system of flexible fabric formwork. For this research 11 different types of beams have been built and tested in total, and their construction methods are illustrated and discussed also (Chapter 7 and Chapter 4 respectively). The designs of the beams are developed through consecutive experiment, analysis, evaluation, and modification process (Chapter 6). For the structural analysis of the beams, the most widely accepted analysis methods are reviewed and adapted (Chapter 8). Based on the evaluations of the analytical results the following variables of the beams are modified through the development of the beam designs: The effect of Compression Steel Mesh in Flange Stress Distribution Around Anchorage; Vertical and Horizontal Web Geometry Varying Depth of Flange Steel Content Also it is a part of the current research’s aim to look at the possible application of the current design methods for the design of the fabric formed beams that are discussed in this research. Thus the experimental results are compared with the results which are calculated from the standard design methods suggested by the British Standard Code of Practice (BS8110) (Chapter 9). Computational finite element (FE) analysis is carried out where more intensive analysis is required (Chapter 10). The results of the FE analysis are also compared with the theoretical and experimental results for the verification purpose. The material efficiency of the beam in its final form is assessed through the embodied energy analysis, which compares the total embodied energy consumed through the construction of the beam with a virtual beam that is designed in accordance with the BS8110 (Chapter 11). The analysis indicates that the total embodied energy of the fabric formed beam is about 20~40% less in comparison with the beam designed in accordance with the BS8110. This thesis has the purpose to illustrate and provide the practical information on the design and the construction process of the fabric formed beams, which can be used as a reference to the future research and construction.

Applying lateral confinement to concrete columns using fibre-reinforced polymer (FRP) composites is a very promising technique. FRP rupture is the typical failure mode of FRP wrapped columns under axial compression. numerous experiments have shown that the FRP rupture strain in an FRP wrapped circular column is significantly lower than the FRP ultimate rupture strain determined from flat coupon test of FRP. Despite a large number of studies on the application of FRP confined columns, the mechanisms and level of lower-than-apparent FRP rupture strain still remain unclear. This thesis presents theoretical, Numerical and experimental studies aiming at developing a deeper understanding of the fundamental mechanisms of this phenomenon. A comprehensive literature review was presented providing the background on FRP confined columns, material properties of FRP composites as well as some factors which may lead to premature FRP rupture. A FE analysis was conducted to investigate the FRP hoop strains in the split-disk test, explaining for the first time that the fundamental mechanism of the lower FRP rupture strain in the split-disk test than in the flat coupon test is because strain localisation due to geometric discontinuities at the ends of the FRP and bending of the FRP ring at the gap due to change of curvature caused by the relative moment of the two half disks, as the FRP (as a brittle material) ruptures once the maximum strain at one of these locations reaches the FRP rupture strain. A list of contributory factors affecting the apparent FRP rupture strain in FRP wrapped columns were next identified and classified. An analytical solution was developed to investigate the influence of the triaxial stress state on the FRP strain efficiency, this factor has been shown to have a potentially significant effect on the failure of the FRP wrap but considerable discrepancies exist between predictions using different failure criteria so further research has been identified in this area. FE models were developed to examine the effect of the geometrical discontinuities on the strain efficiency of FRP jackets in FRP wrapped concrete-filled circular steel tubes and FRP wrapped concrete columns. It is demonstrated that severe FRP hoop strain concentrations occur in very small zones near the ends of the FRP wrap in both types of FRP wrapped columns, leading to premature FRP rupture and thus lower strain efficiency. The combined effects of end constraint and FRP overlap on the behaviour of FRP wrapped concrete columns was investigated using a three dimensional FE model considering one half of the length of an FRP-wrapped concrete cylinder. The results have shown that the frication between both ends of a column and the loading platens provides constraints to the ends of the column, but this constraint has little effect on the strain concentration caused by the geometrical discontinuities of the FRP overlap, though the ultimate axial strain of the FRP wrapped columns can be significantly overestimated if the end constraints are not considered.

It is crucial for a building to maintain structural stability when subjected to multiple and sequential extreme loads. Safety and economic considerations dictate that structures are built to resist extreme events, such as a earthquakes, impacts, blasts or fires, without collapse and to provide adequate time for evacuation of the occupants. However, during such events, some structural damage may be permissible. Design codes do not account for the scenario where two extreme events occur consecutively on a structure nor do they address the situation of the structure having some initial damage prior to being subjected to a fire load. This work begins by detailing the major inconsistancies between designing reinforced concrete structures for extreme mechanical loads and designing for fire. The material behaviour and traits of the constitutive parts (i.e. the concrete and the steel), including post yielding behaviour, thermal relationships and their interaction with each other are all explored in detail. Comprehensive experimental and numerical investigations are undertaken to determine whether, and to what extent, phenomena such as tensile cracking and loss of the concrete cover affect the local and global fire resistance of a member or structure. The thermal propagation through tensile cracks in reinforced concrete beams is examined experimentally. A comparison is made between the rate of thermal propagation through beams that are undamaged and beams that have significant tensile cracking. The results show that, although small differences occur, there is no significant change in the rate of thermal propagation through the specimens. Consequently, it is concluded that the effects of tensile cracking on the thermal propagation through concrete can be ignored in structural analyses. Significantly this means that analyses of heated concrete structures which are cracked can be carried out with heat-transfer and mechanical analyses being conducted sequentially, as is currently normal and fully-coupled thermo-mechanical analyses are not required. The loss of concrete cover and the impact on the thermal performance is examined numerically. A comparison is made of the thermal propagation, beam deflections and column rotations between structures that are undamaged and structures that have partial cover loss in a variety of locations and magnitudes. Results show that any loss of cover can lead to unsymmetrical heating, causing larger deflections in both vertical and horizontal directions, which can result in a more critical scenario. It is concluded that the effect of cover loss on the thermal performance of the structure is extremely significant. A new approach to numerically simulating the loss of cover by mechanical means from a member is developed. This new approach provides the user with an extremely flexible yet robust method for simulating this loss of cover. The application of this method is then carried out to show its effectiveness. A large experimental study carried out at the Indian Institute of Technology, Roorkee and separately numerically modelled at the University of Edinburgh. Unfortunately, due to unforseen circumstances, the experimental data available is limited at this time and as a result the validation of the numerical simulation is limited. Through these investigations it is clear that it is necessary to develop a method in enhance the stability and integrity of the concrete when subjected to the scenario of a fire following another mechanically extreme event. Therefore, finally a method is proposed and experimentally investigated into the use of fibres to increase the post crushing cohesiveness of the concrete when subjected to thermal loads. Results show that the fibrous members display an increased thermal resistance by retaining their concrete cover through an enhanced post crushing cohesion. From this investigation, it is concluded that the use of fibrous concrete is extremely beneficial for the application of enhancing the performance under extreme sequential mechanical and thermal loading.

The overall objective of this thesis is to develop a methodology which can be used to investigate the in-service performance of reinforced concrete members subject to shear loading, in order to update assessments of the shear capacity (and therefore the remaining life) of reinforced concrete bridges. To achieve this end tests have been carried out on two types of reinforced concrete members under different types of loading, with the principal response measured being the relative displacement of the top and bottom faces of the member, which has been referred to throughout as the “through-depth displacement”. The first member tested was a two-span continuous beam containing some web reinforcement in its central shear spans. This was loaded in a series of cycles to progressively increasing peak loads, with a few cycles to lower peak loads being carried out after the application of the higher peak loads.